Energy Modelling for Passive House Design
Designing a Passive House is a rigorous process that involves a lot of detailed energy modelling and a variety of design tools.
The primary tool is spreadsheet called the Passive House Planning Package (PHPP) that was developed by the International Passive House Institute in Germany.
Having been refined over many years, the PHPP has proven to be one of the most reliable tools for accurately predicting a building's energy usage.
The PHPP is very detailed but not very nimble.
At the start of a project it's helpful to have a more flexible and design-oriented tool that can be used to test a wide range of design options.
For the early stages of a project we use the DesignPH plugin for Sketchup. It allows us to quickly build a 3D model of our concepts and test whether or not they might meet the Passive House standard.
The 3D interface also allows us to quickly calculate the impact shading from adjacent buildings and trees.
Flixo (Thermal Bridges)
A thermal bridge is any part of a building where heat can escape through a 'bridge' in the insulation.
The bridge might be a piece of lumber or a piece of metal, but they can quickly negate the benefits of the building's insulation if they're not eliminated.
To test the impact of a thermal bridge we use a piece of software called Flixo that calculates the heat flow through specific parts of a building.
In conventional homes there is substantial thermal bridging through every piece of lumber. This thermal image shows the heat escaping through the thermal bridges.